It is proposed that the mechanism for release of secretory granules be studied with biochemical and biophysical techniques. The ultimate objective of the research is to probe for potential physiologic defects in diabetes mellitus and to understand better the secretory process in general. Model endocrine systems (GH-3 cells, catfish pancreatic islet cells, and rat peritoneal mast cells) which can be stimulated or suppressed by drugs and hormones and which contain sufficient tissue for biochemical isolations will be established in vitro. The contractile proteins myosin, actin and tubulin will be purified from the model endocrine systems using standard techniques; changes in the amount or specific properties of these proteins will be sought after acute and chronic stimulation or inhibition of secretion. A search will be made for the newly-discovered tissue proteins dynein and actin-binding protein, which may affect the secretory process. An attempt will be made to correlate or dissociate secretory effects of colchicine and cytochalasin B and the effects of these agents on microtubules and microfilaments. This will be done by comparing the binding of colchicine to endogenous tubulin to inhibition of secretion, and by comparing the secretory effects of a series of cytochalasins to the very different effects of these agents on actin microfilaments in vitro. Contractile proteins will be localized in the cell by established techniques of centrifugation and immunofluorescence. The recent finding of this laboratory that secretory granule membranes bind actin filaments in vitro will be expanded and extended to non-muscle actins.